Conventionally, there has been known an antenna device to be used for a portable wireless apparatus, for example, a cell phone as shown in FIG. 11. FIG. 11 is a view showing an appearance of a portable wireless apparatus mounting a conventional antenna device thereon. A cell phone 400 uses a TDMA (Time Division Multiple Access) method having a diversity function. More specifically, the cell phone 400 has two antennas 401 and 402 and compares received electric field intensities of the antennas 401 and 402 by utilizing a spare time for a communication, thereby selecting either of the antennas which has a higher received electric field intensity.
The antenna 401 is a whip and helical antenna of an extension type, and is operated as a whip antenna when it is extended from a housing and is operated as a helical antenna when it is accommodated in the housing. The antenna 402 is a built-in antenna such as a reverse F antenna.
FIG. 12 is a view showing an appearance of a portable wireless apparatus using a CDMA (Code Division Multiple Access) method. For a radio communication using the CDMA method, a communicating operation is continuously carried out differently from a radio communication using the TDMA method, that is, a spare time is not generated in the radio communication. For this reason, it is hard to implement the diversity function utilizing the spare time In a conventional portable wireless apparatus 500 using the CDMA method, only one antenna is provided. While the only one antenna 501 is a whip and helical antenna of an extension type in FIG. 12, it may be a built-in antenna such as the reverse F antenna.
In the portable wireless apparatus mounting one antenna thereon, however, there is a problem in that the performance of the antenna is considerably deteriorated and quality of the communication is reduced in the case in which the antenna is pressed with a hand or fingers. According to a measurement carried out by the inventors, a receiving sensitivity is deteriorated by approximately 5 dB when a finger is put on the antenna portion, and is deteriorated by approximately 15 dB when the antenna portion is held in a hand as compared with a state in which the finger or the hand does not touch the antenna portion.
In recent years, particularly, an antenna of such a type as to be provided in a housing of a portable wireless apparatus has spread to enhance a designing property and to improve a convenience in a pocket accommodation. In such a built-in antenna, an antenna portion is covered with a hand or fingers more easily than an antenna protruded to an outside so that the problem is much more remarkable.
FIG. 13 is a view showing an appearance of a portable wireless apparatus using a CDMA method having a built-in antenna, A portable wireless apparatus 600 using the CDMA method is a folding type portable wireless apparatus for solving the problem, and has an upper housing 601 and a lower housing 602 which are supported rotatably around a hinge portion 605. A first antenna 603 is provided in the upper housing 601. Moreover, a second antenna 604 is provided in the lower housing 602. In addition, the portable wireless apparatus 600 is provided with opening/closing detecting portions 606 (600a and 600b) for detecting the opening and closing states of the upper housing 601 and the lower housing 602.
FIG. 14 is a diagram showing a structure of an antenna device mounted on the folding type portable wireless apparatus 600. The antenna device is comprising the first antenna 603, the second antenna 604, a change-over switch 608, an RF portion (wireless circuit) 609, a control portion 607 and the opening/closing detecting portion 606.
In many cases, generally, a communication is being carried out in a state in which the portable wireless apparatus 600 is opened. A user holds the lower housing 602 or the hinge portion 605 in a hand, thereby carrying out a communication. For this reason, the hands or fingers of the user touch a tip portion T of the upper housing 601 with difficulty. In the case in which a result of detection carried out by the opening/closing detecting portion 606 is an opening state, therefore, the control portion 607 transmits, to the change-over switch 608, a control signal for connecting the first antenna 603 to the RF portion 609, thereby connecting the first antenna 603 to the RF portion 609.
The first antenna 603 is a one-wavelength dipole antenna in which high quality of a communication can be obtained in a talking state. Moreover, the opening/closing detecting portion 606 is constituted by the permanent magnet 606a provided in the upper housing 601 and the magnetic force detector (for example, a Hall element) 606b provided in the lower housing 602. When the upper housing 601 and the lower housing 602 are closed, the permanent magnet 606a and the magnetic force detector 606b are close to each other so that a magnetic force detected by the magnetic force detector 606b is increased. On the other hand, when the upper housing 601 and the lower housing 602 are opened, the permanent magnet 606a and the magnetic force detector 606b separate from each other. For this reason, the magnetic force detected by the magnetic force detector 606b is reduced. By utilizing this fact, the detection of the opening/closing operations of the upper housing 601 and the lower housing 602 is carried out. The opening/closing detecting portion may have a structure in which the magnetic force detector is provided in the upper housing 601 and the permanent magnet is provided in the lower housing.
In a state in which the portable wireless apparatus 600 is closed, a waiting condition is set in many cases. In the case in which the user holds the portable wireless apparatus 600 in a hand, a position which is hard to touch with the hands or fingers is placed in the vicinity of the hinge portion 605. For this reason, in the case in which a result of the detection carried out by the opening/closing detecting portion 606 is a closing state, the control portion 607 transmits, to the change-over switch 608, a control signal for connecting the second antenna 604 to the RF portion 609, thereby connecting the second antenna 604 to the RF portion 609. Since the second antenna 604 is of an unbalanced power feeding type for radiating an electric wave from a ground pattern on a printed board in which the RF portion 609 is disposed, it has a high radiation efficiency and is suitable for waiting. By detecting the opening and closing states of the portable wireless apparatus 600 and selecting a suitable antenna for the respective states depending on the result of the detection, thus, it is possible to enhance the quality of the communication.
In recent years, moreover, a portable wireless apparatus mounting an image pick-up device (a camera) thereon has spread. There has been known a portable wireless apparatus which mounts a plurality of antennas thereon, detects visual information in the vicinity of the portable wireless apparatus by means of the camera and decides an electric wave propagation environment from the visual information, thereby selecting an antenna (for example, see Patent Document 1). In more detail, the portable wireless apparatus calculates an angle thereof with respect to a perpendicular line from a ground based on an image picked up by the camera and selects the most suitable antenna for a plane of polarization of an electric wave to arrive based on information about the angle, thereby implementing an excellent antenna characteristic.
With the spread of the portable wireless apparatus mounting the photographing device thereon, moreover, a user has demanded the appearance of a portable wireless apparatus having a two-axis hinge mechanism which has conventionally been mounted on a video camera (for example, see Patent Document 2).
FIG. 15 is a view showing an appearance of the portable wireless apparatus mounting the two-axis hinge mechanism thereon. A portable wireless apparatus 700 has such a structure that an upper housing 702 and a lower housing 703 are connected to each other through a two-axis hinge portion 701. Moreover, an image pick-up device (camera) 704 is provided in the lower housing 703. The portable wireless apparatus 700 can be used with the housing opened as in the folding type portable wireless apparatus 600 in the case in which a telephone function is used, and can fix a screen into such a position as to be easily seen (a photographing state) to carry out photographing when the image pick-up device is used. Thus, it is possible to enhance the convenience of the user.
Furthermore, a portable wireless apparatus mounting a plurality of image pick-up devices thereon has been started to appear. By mounting the image pick-up devices, it is possible to properly use the image pick-up devices in the case in which a user himself (herself) is to be photographed and the case in which an object is to be photographed.
(Patent Document 1) JP-A-2001-103002 Publication
(Patent Document 2) JP-A-11-247840 Publication
However, the conventional portable wireless apparatus has the following problems and an improvement thereof has been demanded. More specifically, the potable wireless apparatus having a two-axis hinge mechanism has various using configurations which cannot be obtained by the folding type portable wireless apparatus but the two-axis hinge mechanism. In such using configurations, particularly, it is hard to always maintain high quality of a communication in the portable wireless apparatus using the CDMA method.
In the portable wireless apparatus mounting the image pick-up device thereon, when visual information in the vicinity thereof is detected to carry out a switching control for an antenna, it is hard to maintain the high quality of the communication if the hands or fingers of the user approach the antenna.
The invention has been made to solve the problems and has an object to provide a portable wireless apparatus capable of maintaining high quality of a communication in various using configurations obtained by a two-axis hinge mechanism.